1. Field of the Invention
The present invention relates to the field of computer system interfaces and, more particularly, to the integration between programmer-integrated-development environments (IDEs) and application servers.
2. Description of the Related Art
As is well known, computer files are stored in a storage medium (e.g., disk) using a directory structure. The “address” of a file is the storage location from where it can be retrieved and typically comprises one or more directory segments and a file name. This address is referred to as the “absolute path” of the file. As an example, in a Windows environment, the absolute path “D:\Workspace\Projects\ExampleApplication” identifies a file with the filename “ExampleApplication” stored on the “D drive” of a Windows-based computer in the subdirectory “Projects” of the directory “Workspace”.
The Java 2 Platform Enterprise Edition (J2EE) specification defines a standard architecture that has received widespread industry support and growing customer acceptance, and increased investment focus has been placed on J2EE technology by the industry. In accordance with the Sun J2EE specification, an enterprise application is packaged in a well known archive file format, and the packaged application is called an Enterprise Archive, or EAR file. A typical J2EE application comprises multiple archive files, referred to as “modules” and “utility JARs.” These archives may also be known as “nested” archives. When an enterprise application is deployed on an application server, it is common for the top level EAR file to be expanded into a directory structure on disk. The nested archives in the expanded EAR file are then located as files or directories directly under the root directory location of the EAR file.
A module in the context of J2EE architecture is a specialized kind of JAR file, containing Java classes and a deployment descriptor. A deployment descriptor is a configuration file that contains deployment information instructing an application server running the program how to deploy the enterprise application. A utility JAR file is a common JAR file that contains compiled Java classes that are referenced by Java classes in one or more other module or JAR files in the enterprise application. As noted above, all modules and utility JARs are relative to the EAR file that contains them.
It is not uncommon for the nested JAR files to themselves contain nested JAR files. An example is a WAR file as described in the Sun Java Servlet Specification, v2.2, by Sun Microsystems (Dec. 17, 1999). In addition to web pages and other assorted files (e.g., graphics), a WAR file may contain “libraries”, which are JAR files containing compiled programming code to be utilized by the web application.
IDEs often make use of the concept of a “project”. A project can be defined as a collection of files grouped together under a common project name for a common development effort. Typically all files in a project are stored relative to a single directory in the file system. The environment can contain many projects. A flexible IDE will allow a project to exist in any location on the file system.
Most IDEs can be extended by specialized developer tools. For example, tools exist which layer over a base IDE to provide support for J2EE application development. Additionally, these tools can deploy developed J2EE applications on an application server locally installed within the IDE. In an optimal environment, the application server will run the applications using the files as they are stored in the IDE, so that the programmer can debug and modify the original files.
A problem arises, however, because the directory structure and project locations in the IDE do not fit the J2EE mold. For example, the IDE can create one project for an EAR file, and separate “referenced” projects for each module and utility JAR file in the EAR file. Each of these projects can be located in an arbitrary location, which is external to the EAR project. The highest-level project, (the project that “contains” the nested archives, or contains references to other projects that conceptually represent nested archives) is referred to generically as a “container project”. Two examples of container projects in a J2EE environment are EAR projects, that represent enterprise applications or EAR files, and Web projects, that represent web applications or WAR files. The application server, however, expects the files to be in a hierarchical directory structure as noted above. Moreover, the location of these externally-stored referenced projects may differ from one developer's machine to the next (also a function of flexibility in the IDE), and the referenced file would therefore be difficult to find by the container project. Therefore, a solution is needed which integrates the development environment with the application server such that the server can use the files as they exist in the projects of the development environment.
A sub-optimal solution is to copy the contents of the project in the IDE into a separate EAR file, and launch the server on that file. This involves actually generating a deployed EAR file from the project contents in the IDE for the Enterprise Application. This external EAR file is then installed and started on the application server. This solution is not optimal because of the duplication of files, and because the developer is not able to debug the original files (those that are actually being developed), but instead can only debug the copies. Many existing application server tools currently use this approach.
Another solution developed for use with Websphere by IBM involves the concept of “loose files”, also known as “loose modules” or “loose archives.” Loose files are simply files that are stored outside of the directory structure of the expanded EAR, i.e., they are not contained in a subdirectory of the EAR. Examples of loose archives include the above described project references from an EAR project to a project that represents a J2EE module or utility JAR, and references from a J2EE web project to a project that represents a library in a WAR file. In this solution, rather than store the nested archive contents within the file structure of the EAR file, contents are placed in separate projects. This enables the tools to adapt the project structure of the IDE to compose an enterprise application for deployment.
It is quite common for tool and application server vendors to store additional meta-data in an additional file inside a J2EE archive. This meta-data may contain runtime information that goes above and beyond the standard specification. This vendor specific file is called an “extensions” file, because it extends the specification.
To coordinate the interaction between projects making up an enterprise application and mapping the loose files for use at runtime, prior art systems utilize the above-described file structure and use the extensions file of a container project (e.g., EAR project) to store the absolute paths of the referenced projects. Thus, for example, a tag in a file in a particular project directs the application server running the enterprise application to retrieve particular content from a particular absolute address. As long as the address information of the file is a valid address for the machine on which the enterprise application is running, the enterprise application will function properly.
This implementation has known limitations, however. For one, it is not “team friendly”. For example, suppose Developer A stores files pertaining to the development of enterprise application “X” at a location/path “C:\Workspace” on his workstation. Assume further that Developer D stores files related to development of enterprise application X on her computer at a location/path “Q:\Workspaces\Development\Workspace.” During development of the EAR for enterprise application X, the system places a tag in the application extensions file that directs the enterprise application to retrieve a web module that has an absolute path of C:\Workspace\ExampleWeb\WebContent. Developer A then stores the EAR project, and all its referenced projects, into a repository used by the team members for development purposes.
Now Developer B retrieves the EAR project, and all its referenced projects from the repository and loads it into her workspace. Since the tag in the extensions file will point to a non-existent or invalid location relative to Developer B's computer (C:\Workspace\ExampleWeb\WebContent) the test will fail and indicate that the path is non-existent.
Tools exist to correct this problem. Specifically, developers'tools can identify the existence of an incorrect path and replace it with the correct path, which is derived by the IDE. For example, the developer's tools can locate Developer B's workspace and update the tag to direct it to the absolute path Q:\Workspaces\Development\Workspace\ExampleWeb\WebContent, which is where the file “WebContent” will be found. However, this modifies the original extensions file in the EAR project. Developer B may either discard this updated file when testing is completed (which will require the same process to be followed the next time Developer B attempts to test the EAR) or the modified file can be saved and checked into the repository, which will cause a similar problem for Developer A next time he attempts to test the file. This is time-consuming for the developer, and also creates confusion for the developer. The confusion arises because whenever the file is modified, it is marked as “dirty” (modified) and in need of synchronization with the repository. The developer sees this visual cue and must make a decision to either ignore it or check the file into the repository. Moreover, if any valid changes are also made in the extensions file, then when the developer goes to synchronize the file with the repository, the valid differences must be differentiated from the changes made only as a result of the absolute paths.
The inclusion of the absolute paths also presents a problem when the EAR file is exported from the development environment to be deployed on a live production server. Since these absolute paths are only utilized for testing, the absolute paths must be removed from the extensions file contained in the EAR file as part of the process of packaging the EAR for deployment. If the absolute paths are not stripped out of the EAR file, then the running production server (the server running the deployment version) will try to load nested archives from these now-non-existent absolute locations, causing an error. This implies that developers are required to use the export tools provided for packaging the EAR. In some instances, however, developers may prefer to use their own customized program scripts to package the EAR, instead of the provided tools. In this case, the developer would need to be aware of the absolute path tags in the extensions file and would need to also have special code to strip these tags during packaging.